For decades, fractures and dislocations of the cervical spine have been treated by applying cervical traction. Traction is applied utilizing tongs which typically have spring loaded pins that penetrate the skin and engage the outer table of the skull of the patient, a strand connected to the tongs applying the necessary traction force. Sometimes the tongs are articulated, such as shown U.S. Pat. No. 3,401,688, to apply a clamping force with the pins rather than spring loading of the pins.
Most existing tongs and related components are made of stainless steel. Because of that, the tong systems blocks CT scans of the brain, and also interfere with MRI scanning of the brain, although the MRI interference may be solved by using titanium as the material of the tong and pins. Obtaining clear images of the brain, especially CT scans, is very important for most patients with cervical injuries since the mechanism of injury that causes the cervical distress is usually a blow to the head, which can also cause brain injury. Using traditional tongs, a neurosurgeon or orthopedic surgeon must go with the patient to radiology and remove the tongs while the patient is having a scan, then reapply them. This is time consuming for the physician and dangerous for the patient. The other alternative is to delay stabilizing the patient with tongs until CT scans can be obtained, which is even more dangerous to the patient.
According to the present invention, cervical traction tongs are made of a material which is entirely MRI and biologically compatible, and CT transparent. Only the pointed pin tips are not completely CT transparent, and those pin tips are radiolucent, so that they result in minimal artifact (about equal to that of bone) in resultant film so that there is no interference with diagnosis. Preferably the pins are made of single crystal alumina ceramic, such as shown in U.S. Pat. No. 4,612,930, the disclosure of which is hereby incorporated by reference herein.
The typical materials of which the tongs and skull pins can be made are a wide variety of MRI compatible and CT transparent plastics. The plastic must have sufficient elasticity, however, so that the arms of the tongs can apply constant pressure of the pin points against skull bone. There are a wide variety of materials that can be used for this purpose, some examples of which are: glass filled (e.g. 35%) ULTEM (a trademark of General Electric) polyesteramide, or glass or carbon fiber filled polysulfone, or fiber reinforced tempered nylon.
While the tongs according to the invention solve the problem of interference with brain scans and the like, because plastic--of which the pin bodies are made--is not as strong as the conventional pin and tong materials such as stainless steel and titanium, it is necessary to provide adjustability of the width of the tongs; that is the spacing between the pointed tips of the pins must be adjustable. This is accomplished by providing the tongs as interconnected first and second arms, one being a mirror image of the other. At a first end of the arms they have means for receipt of the bodies of the pins so that the pins extend through the arms with the tips pointing toward each other. At the second ends of the arms they have cooperating structures which allow the relative angular position of the arms to be adjusted, yet allowing the arms to be positively held in place in the position to which they have been adjusted, so that the spacing between the pin tips can be changed so as to minimize the bending moment applied to the pin bodies. That is the effective length of the pins is kept short so that the bending moment that is applied thereto is minimized.
Preferably the second ends of the arms are formed by enlarged circular end terminations each having generally radially extending serrations, the serrations of the first arm mating with the serrations of the second arm. Fastening means, such as a bolt of MRI and biologically compatible and CT transparent material, passes through a central opening in the enlarged end terminations, and is held in place by a nut of similar material. An arcuate elongated opening is provided in each of the arms at a portion thereof remote from the first ends of the arms, which is adapted to receive the strand which is used for applying the traction force to the tongs. The pins preferably include torque limiting caps for applying torque, such as shown in U.S. Pat. No. 4,838,264, the disclosure of which is hereby incorporated by reference herein.
The tongs and pins according to the present invention are preferably packaged in sterile packaging, and need only be used for one patient. That is, after they are removed from the sterile packaging and used in association with one patient, they may be thrown away. This is so because while the material utilized in the construction of the tongs is CT transparent, etc., it is relatively inexpensive (compared to stainless steel and titanium), and while it is capable of sterilization, it is most suitably not sterilized for reused.
According to another aspect of the present invention, a method of treating a human with an injury to the cervical spine is provided, the method comprising the steps of: (a) Adjusting the spacing between the pin tips by adjusting the relative angular position of the curved arms so as to conform to the skull width so that minimal bending moment is applied to the skull pins. (b) Holding the arms together in the desired position to which they have been angularly adjusted. (c) By applying torque to the skull pins, causing the pointed tips thereof to penetrate the skin of the human and engage the outer table of the human's skull. (d) Applying tension to the human's cervical spine by applying a force to the tongs. And, (e) without disturbing the tongs, CT scanning or magnetic resonance imaging the patient's skull. Step (a) is typically practiced by moving the serrations on the end terminations of the arms until the desired serrations for providing the desired spacing between the skull pins cooperate, and then fastening the end terminations together in that position. Step (c) is preferably practiced by rotating the torque limiting caps, the tong arms having sufficient elasticity to provide constant pressure urging the pointed pin tips against the patient's skull.
It is the primary object of the present invention to provide an advantageous cervical traction tong, and method of utilization thereof. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.